System for accurately increasing the range of gun projectiles

ABSTRACT

The present invention is a gun system which utilizes rocket assisted projectiles and accurately controls their placement. The projectile is fired by a gun and actual trajectory variables are compared in a computer with desired trajectory conditions. If there is a difference, the firing time of the rocket is altered to make the actual trajectory variable correspond to the desired condition. A radar system is utilized by the computer to obtain the trajectory information. A transmitter is connected to the computer to send the firing signal to a receiver mounted in the projectile.

waited Stts Patet [1 1 McAlexander et al.

[ Sept. 11, 1973 SYSTEM FOR'ACCURATELY INCREASING THE RANGE OF GUN PROJECTILES [75] Inventors: Robert L. McAlexander, Saratoga,

Calif.; Lilburn G. Stout, Falmouth, Va.

' [73] Assignee: The United States of America as represented by the Secretary of the Navy, Washington, DC.

22 Filed: July 9, I969- [21] Appl. No.: 844,727

[52] US. Cl 244/3.l4, 102/49.7, 244/322 [51] int. Cl. F421! 13/30 [58] Field of Search 102/49.7; 244/322,

[56] I References Cited UNITED STATES PATENTS 2,629,289 2/1953 Hunter 89/41.7 SW

May et al 244/322 Plumley 244/322 X Primary ExaminerVerlin R. Pendegrass AttorneyEdgar J. Brower, Arthur L. Branning, T. 0. Watson, Jr. and T. J. Madden 5 7] ABSTRACT The present invention is a gun system which utilizes rocket assisted projectiles and accurately controls their placement. The projectile is fired by a gun and actual trajectory variables are compared in a computer with desired trajectory conditions. If there is a difference, the firing time of the rocket is altered to make the actual trajectory variable correspond to the desired condition. A radar system is utilized by the computer to obtain the trajectory information. A transmitter is connected to the computer to send the firing signal to a receiver mounted in the projectile. V

7 Claims, 3 Drawing Figures PATENTEB 7 75 mSow wzEE E mwZmumm INVENTORS a & L/LBUEW a. $700? ROBERT L. McALEXANDER \Zfl WM. O. A/%

ATTORNEY SYSTEM FOR ACCURATELY INCREASING THE RANGE OF GUN PROJECTILES STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION Field of the Invention This invention is directed to the field of ballistic control. More particularly, this invention is directed to a system which accurately increases the range of gun projectiles.

Description of the Prior Art No effective inexpensive method of assuring the accurate placement of projectiles while at the same time increasing their range is found in the prior art.

One type of prior art system for assuming accurate placement of projectiles utilized an explosive charge which was mounted on the side 'of the missile. This method however has a number of inherent disadvantages. The first disadvantage is that if the explosive is not facing in the proper direction, the projectile will be driven off of the desired trajectory. The hardware necessary for this operation is complex and expensive. In addition, the explosive charge is exhausted when once fired and cannot be used to increase the range of the projectile. Finally, the explosive charge cannot propel the projectile forward. Thus, if the projectile is subjected to a strong headwind or down draft, the charge will not enable the projectile to maintain the desired trajectory.

Ordinary guided missiles carrying explosive warheads do not offer the advantages obtainable with accurately fired guns. Guided missiles are extremely expensive and bulky. These missiles require elaborate control systems and specifically designed launching areas. They are not compatable with conventionally equipped ships.

SUMMARY OF THE INVENTION The present invention accurately controls the placement of rocket-assisted gun projectiles and offers significant advantagesover the prior art. The projectile utilized is simply designed and is very rugged. Its clost is minimal in relation to that of guided missiles. It can be fired from conventional guns and control can be achieved at almost any point in its trajectory.

The inventive system utilizes rocket-assisted projectiles. When the projectiles are fired from the gun, a radar tracker follows their trajectory and feeds it to a computer which compares actual trajectory variables with the desired trajectory conditions. If there is a difference the computer will change the time at which the initiating signal is sent to a transmitter. The transmitter in turn sends this signal to the projectile to activate the booster rocket to bring the actual trajectory variable into correspondence with the desired trajectory condition.

It is an object of the present invention to provide an inexpensive rugged system for accurately controlling the placement of gun-launched projectiles.

It is a further object of this invention to provide a system which will provide post launch, inflight control of gun-fired projectiles from a ground based position.

It is a further object of the present invention to provide a system capable of compensating inflight for errors incurred during launch. Such errors include gun jump, variation in initial velocity, variation in elevation angle andany other measurable gun launch error.

Other objects, advantages and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic of the inventive system;

FIG. 2 is a cross-section of the rocket-assisted projectile utilizes; and

FIG. 3 is a circuit diagram of the receiving and firing circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing and in particular FIG. 1 which shows the inventive system and various trajectories of the rocket-assisted projectile 11. The inventive system utilizes a gun 12 to fire the projectile 11. A computer 13 is connected to the gun as well as to the radar 14 and transmitter 15.

Initially, the gun is aimed and its firing angle fed to computer 13. When the gun is fired, a trigger signal is sent to a clock in the computer. Ten seconds after firing, the computer activates the radar 14 which sends a pulse to the projectile 11. This pulse is reflected off the projectile and received by the radar. The radar gives a reading of the azimuth and elevation of the projectile. This reading is a measure of the actual launch velocity (which is justone of the possible launch errors) and trajectory time of the projectile and is fed to the computer where its impact point is calculated. The desired impact point is compared to the predicted impact point and an initiation time is generated to insure the desired range is reached. The initiation signal is sent together with the output from a computer clock to a coincidence circuit. When the clock has counted off the requisite time, the signal is sent to the transmitter.

The computer is programmed for all the desired trajectories and impact points of all the firing angles and muzzle velocities of the gun. This information is generated in the computer as a function of time. The computer thus knows that at a firing angle of 30 the rocket motor must be pulsed at a certain time, such as 15 seconds after firing in order to land at the desired impact area.

If the desired and actual trajectory and impact points differ, then the time that the pulse is sent to start the rocket in the projectile 11 must differ.. Thus, assuming a desired trajectory of 30 at the 10 second point and a firing time of 15 seconds (trajectory A, FIG. 1), the projectile will go beyond the impact point if the actual trajectory angle is 35 (trajectory B) at the 10 second point. If the actual angle is 25 (trajectory C) at the 10 second point, the projectile will fall short of the impact area.

The computer provides compensation for these variations and changes the firing time of the rocket when there is a difference between the actual and desired trajectory variables. Thus as seen in FIG. 1, if the desired firing of the rocket occurred at the apex of the unassisted trajectory, the actual firing must occur after this point when the actual trajectory is 35 at seconds. Similarly, the actual firing must occur before this point when the actual trajectory is 25 at 10 seconds. At the 35 firing point the rocket motor vector will have a down thrust which will shorten the range while at the 25 firing point the rocket motor vector will have an upward thrust which will increase the projectiles range.

The projectile 11 utilized is shown in detail in FIG. 2. The projectile is comprised of a nose cone 21, an explosive chamber 22 and'a rocket chamber .23. An explosive 24 and a detonator 25 are contained within the explosive chamber 21. A rocket is formed in the rocket chamber and comprises solid fuel 26, firing squib 27 and nozzle 28.

Eccentric plug 29 and O ring 30 seal the rocket. These items serve two purposes. When the projectile is in storage, they protect the inside of the rocket chamber. When the projectile is fired, they keep the explosive force out of the chamber and prevent premature ignition of the rocket. I

The ignition train of the rocket is also mounted inside the rocket chamber 23. The train includes half-wave antenna 31 which is encased in epoxy or the like for protection and a support plug 32 which holds the receiving and firing circuit 33 and connects it with the antenna. The receiving and firing circuit is connected through a coaxial cable 34 to the squib 27.

The receiving and firing circuit is shown in more detail in FIG. 3. It includes an F.M. receiver 41, a frequency discriminator 42 and a level detector 43 connected in series to the firing circuit 44. A power supply 46, centrifugal switch 47 and a delay circuit are also connected in series to the firing circuit 44v which is in turn connected to the squib 27.

The centrifugal switch disconnects the power supply, which is generally a battery, from the firing circuit when the projectile is in storage. This preserves the charge on the battery and protects against premature firing of the rocket.

Turning now to the operation, the gun will fire the projectile and impart a spin and a forward velocity to it. Asthe spin builds up the eccentricity of the plug 29 will cause it to loosen. It will then move out of the nozzle area and away from the projectile exposing the antenna 31.

The spin of the projectile will also close centrifugal switch 46 and begin the charging of a capacitor in the firing circuit. The delay circuit 47 comprises a resistor which controls the time constant of the capacitor. This time constant is made long enough to prevent possible ignition of the rocket until it is well beyond the gun launch area.

At the time selected for firing of the rocket the transmitter sends a frequency modulated signal to the projectile. This signal is picked up by the receiver through antenna 31 and passed to frequency discriminator 42 and level detector 43. The discriminator and level detector protect against spurious signals and insure that the rocket is not improperly ignited.

The signal passed by the level detector closes a switch in the firing circuit. This connects the firing capacitor to the squib. The squib is then ignited and in turn ignites the rocket.

Thus it is seen that a new and improved system for increasing the range and accuracy of gun launched projectiles has been provided. The system is rugged and simply constructed.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. What is claimed is:

'l. A system for controlling the placement of a gunlaunched projectile comprising:

a projectile adapted to be launched from a gun;

booster rocket means incorporated in said projectile for imparting additional thrust along the longitudinal axis of the projectile subsequent to the launching of said projectile from said gun; means located remote from said projectile for measuring actual projectile trajectory parameters; computer located remote from said projectile responsive to said measuring means which utilizes the measured trajectory parameters to provide an indication of when said measured trajectory parameters differ from the desired projectile trajectory parameters and which generates an initiate signal when the measured variables and the desired conditions differ; a transmitter connected to said computer and operable to send said initiate signal to said projectile; said projectile further comprising a radio receiver to receive the initiate signal from said transmitter;

Wherein the rear section of said projectile forms a booster rocket which is actuated by said initiate signal received by said radio receiver to provide additional thrust to said projectile along its longitudinal axis.

2. A system as in claim 1 further comprising a squib connected to said radio receiver for firing said rocket booster.

3. A system in claim 2 wherein said rocket booster includes:

a nozzle through which ignited rocket fuel is directed; and

solid rocket fuel for powering said rocket booster;

said radio receiver being mounted in said nozzle.

4. A system as in claim 3 further comprising an eccentric plug mounted in said nozzle to protect said radio receiver and to prevent premature ignition of said rocket.

5. A system as in claim 4 further comprising a centrifugal switch connected to said squib; and

a power supply connected to said centrifugal switch for providing energy to ignite said squib;

said centrifugal switch being operative to prevent power from reaching said squib until sufficient spin is imparted to said projectile.

6. A system as in claim 5 further comprising:

a discriminator connected to radio receiver to protect the system from erroneous ignition signals; and

a level detector connected to said discriminator and said squib to further insure that the squib is ignited at the proper time.

7. A system as in claim 6 further comprising a delay circuit connected between said centrifugal switch and said squib to prevent-premature ignition of said squib.

. IF I 4' I. 

1. A system for controlling the placement of a gun-launched projectile comprising: a projectile adapted to be launched from a gun; booster rocket means incorporated in said projectile for imparting additional thrust along the longitudinal axis of the projectile subsequent to the launching of said projectile from said gun; means located remote from said projectile for measuring actual projectile trajectory parameters; a computer located remote from said projectile responsive to said measuring means which utilizes the measured trajectory parameters to provide an indication of when said measured trajectory parameters differ from the Desired projectile trajectory parameters and which generates an initiate signal when the measured variables and the desired conditions differ; a transmitter connected to said computer and operable to send said initiate signal to said projectile; said projectile further comprising a radio receiver to receive the initiate signal from said transmitter; Wherein the rear section of said projectile forms a booster rocket which is actuated by said initiate signal received by said radio receiver to provide additional thrust to said projectile along its longitudinal axis.
 2. A system as in claim 1 further comprising a squib connected to said radio receiver for firing said rocket booster.
 3. A system in claim 2 wherein said rocket booster includes: a nozzle through which ignited rocket fuel is directed; and solid rocket fuel for powering said rocket booster; said radio receiver being mounted in said nozzle.
 4. A system as in claim 3 further comprising an eccentric plug mounted in said nozzle to protect said radio receiver and to prevent premature ignition of said rocket.
 5. A system as in claim 4 further comprising a centrifugal switch connected to said squib; and a power supply connected to said centrifugal switch for providing energy to ignite said squib; said centrifugal switch being operative to prevent power from reaching said squib until sufficient spin is imparted to said projectile.
 6. A system as in claim 5 further comprising: a discriminator connected to radio receiver to protect the system from erroneous ignition signals; and a level detector connected to said discriminator and said squib to further insure that the squib is ignited at the proper time.
 7. A system as in claim 6 further comprising a delay circuit connected between said centrifugal switch and said squib to prevent premature ignition of said squib. 